11 documents found in 379ms
# 1
van den Ende, Martijn
Abstract: Intergranular pressure solution creep is an important deformation mechanism in the Earth’s crust. The phenomenon has been frequently studied and several analytical models have been proposed that describe its constitutive behavior. These models require assumptions regarding the geometry of the aggregate and the grain size distribution in order to solve for the contact stresses, and often neglect shear tractions. Furthermore, analytical models tend to overestimate experimental compaction rates at low porosities, an observation for which the underlying mechanisms remain to be elucidated. Here we present a conceptually simple, 3D Discrete Element Method (DEM) approach for simulating intergranular pressure solution creep that explicitly models individual grains, relaxing many of the assumptions that are required by analytical models. The DEM model is validated against experiments by direct comparison of macroscopic sample compaction rates. Furthermore, the sensitivity of the overall DEM compaction rate to the grain size and applied stress is tested. The effects of the interparticle friction and of a distributed grain size on macroscopic strain rates are subsequently investigated. Overall, we find that the DEM model is capable of reproducing realistic compaction behavior, and that the strain rates produced by the model are in good agreement with uniaxial compaction experiments. Characteristic features, such as the dependence of the strain rate on grain size and applied stress, as predicted by analytical models, are also observed in the simulations. DEM results show that interparticle friction and a distributed grain size affect the compaction rates by less than half an order of magnitude. The zip-file Van-den-Ende_2017.018.zip contains several folders with raw data from the laboratory experiments, output data from Discrete Element Method simulations, and Python 2.7 script files that read and process these data. All data are stored in ASCII format.
# 2
Trippetta, Fabio • Carpenter, Brett M • Mollo, Silvio • Scuderi, Marco M. • Scarlato, Piergiorgio • (et. al.)
Abstract: Here we report the raw data of the physical properties of carbonate samples collected along the Monte Maggio normal Fault (MMF), a regional structure (length ~10 km and displacement ~500 m) located within the active system of the Apennines (Italy). In particular, we report results coming from large cores (100 mm in diameter and up to 20 cm long) drilled perpendicular to the fault plane made of Calcare Massiccio (massive limestone) and Bugarone fm (limestone with 8.3 % of clay). From these large cores, we obtained smaller cores, 38 mm in diameter both parallel and perpendicular to the fault plane, that have been used for experiments. We have divided the rock samples in four categories following the fault architecture. The four structural domains of the fault are:1) the hangingwall (HW) made of Bugarone fm that is still preserved in some portions of the fault, 2) a Cemented Cataclasite (CC) and 3) a Fault Breccia (FB) that characterize the cataclastic damage zones and 4) the correspondent undeformed protolith of the footwall block made of Calcare Massiccio. Raw data reported here are those used for drawing Figures 5, 6, 8 and 9 of the paper “Physical and transport property variations within carbonate- bearing fault zones: Insights from the Monte Maggio Fault (central Italy)”, http://doi.org/10.1002/ 2017GC007097 by Trippetta et al. Dataset_Fig05.txt reports P- and S-wave velocities (in km/s) of the described samples at pressure from 0.1 MPa (ambient pressure) up to 100 MPa at ambient temperature in dry conditions and the corresponding Vp/Vs ratio. Experiments have been performed by using the permeameter at the HP-HT Laboratory of experimental Volcanology and Geophysics at INGV (Rome). Dataset_Fig06.txt reports permeability data (in m^2) on the same type of samples of fig05 for the same range of confining pressure at ambient temperature. Pore pressure values athletes each confining pressure step are indicated in the file. Data have been again acquired with the permeameter. Dataset_Fig08.txt reports P-wave velocity data (in km/s) vs depth (in m), recorded on the portion that crossed the Calare Massiccio fm of three boreholes drilled in the Apennines: Varoni 1, Monte Civitello 1 and Daniel1. Data have been obtained by digitalizing each pdf file of the boreholes mentioned above, that are available at http://unmig.sviluppoeconomico.gov.it/videpi/videpi.asp. Once digitalized, respect to the original pdf file, velocity data have been simply converted from um/f to km/s. Dataset_Fig09.txt reports values of the maximum, minimum and average values of Critical fault nucleation length (in m) at each corresponding depth (in m) and applied confining pressure (in MPa). Critical nucleation lengths have been calculated by using the equations described in the text of the Trippetta et al paper and by using the elastic parameters calculated from data reported here. Data on earthquakes-depth distribution of the 2009 L'Aquila sequence can be found on Chiaraluce et al. (2011).
# 3
Sembroni, Andrea • Kiraly, Agnes • Faccenna, Claudio • Funiciello, Francesca • Becker, Thorsten W. • (et. al.)
Abstract: We present videos and figures from 22 scaled analogue models used to investigate the interactions between a density anomaly rising in the mantle and the lithosphere in a Newtonian system. The experimental setup consists of a two layers viscous lithosphere-upper mantle system obtained by using silicone putty-glucose syrup in a tank sized 40 cm × 40 cm× 50 cm. Glucose syrup (i.e., mantle) is a Newtonian, low viscosity, high-density fluid while silicone putty (i.e., lithosphere) is a visco-elastic material that behaves in a quasi-Newtonian fashion. The mantle upwelling (i.e., plume head) is produced by a high viscosity, low-density silicone sphere with a constant radius (15 mm) rising through the mantle at an average rise velocity of ~2.6 mm/s. A side-view camera images the ascending path of the sphere, allowing to track the sphere location and compute its velocity. A top-view, 3-D scanner records the evolution of topography from which the lithospheric uplift rate is inferred. All details about the model set-up, modeling results and interpretation are detailed in Sembroni et al. (2017). The additional material presented in this publication includes 2 tables, 5 figures, and 23 time-lapse movie. The rheological properties of materials used in each model are listed in Table 1.Table 2 is an excel file where the raw data of the models are specified (i.e., bulge width, topography, and uplift rate). Such data have been obtained by the 3-D scanner and then processed by a MATLAB code.Figure 1, Figure 2, Figure 3, Figure 4, Figure 5 represent the 2-D topography evolution of the bulge in each experiment. Images have been grouped by considering the different experimental setups (i.e., homogeneous continental lithosphere - Figure 1, homogeneous oceanic lithosphere - Figure 2, low viscous decoupling layer - Figure 3, intermediate viscous decoupling layer - Figure 4, high viscous decoupling layer - Figure 5). Such figures consist of topographic profiles extracted from the surface obtained by the 3-D scanner in four different time steps (red numbers in the figures). 22 side-view videos (from Movie 1 to Movie 22) show the progress of the models from the releasing to the impingement of the sphere beneath the plate. The velocity of the video has been accelerated by a factor of 7. While, the first 22 movies show the evolution of the experiments, Movie 23 shows the mantle convective flow associated to the ascending path of the mantle upwelling. Such flow has been detected by tracking the bubbles inside the syrup. In this model, no lithosphere has been placed on top of the syrup.
# 4
Ritter, Malte C. • Rosenau, Matthias • Oncken, Onno
Abstract: This dataset is supplementary material to the article of Ritter et al. (2017). In this article, the similarity of fault propagation work in analogue sandbox experiments to natural fault networks is investigated through measurements in a strike-slip sandbox and in a ring-shear-tester. The transient shear strength of the samples is measured for different fault lengths and from this the work is determined. For a detailed description of the procedure and the set-up please see Ritter et al. (2017). The data available in this supplementary publication are:• For the strike-slip experiments three video sequences of the deformation together with the evolution of boundary force for fault lengths of 20 cm, 30 cm and 40 cm. The videos show the curl of the deformation field, determined by Digital Image Correlation of top-view video images. These files are in AVI-format and included in the zip folder 2017-005-Ritter-movies.zip.• A folder containing force vs. displacement measurements for each experiment (2017-005-Ritter-forces.zip). These are 25 ASCII-files that contain two columns of numerical data: the first column is the displacement in meter; the second column is the corresponding force in newton. The files are named according to the following pattern: <fault length in meter>_<experiment number>.asc• A Matlab script to load the force files and calculate the work. This file is called “plotwork.m” and calls the Matlab function “work.m”, which does the actual calculations. These files have been tested in Matlab version 2012b. The surface deformation data are available upon request.
# 5
Ritter, Malte Christian • Santimano, Tasca • Rosenau, Matthias • Leever, Karen • Oncken, Onno
Abstract: This dataset is supplementary to the article of Ritter et al. (2017). In this article, a new experimental device is presented that facilitates precise measurements of boundary forces and surface deformation at high temporal and spatial resolution. This supplementary dataset contains the measurement data from two experiments carried out in this new experimental device: one experiment of an accretionary critical wedge and one of Riedel-type strike-slip deformation. For a detailed description of the set-up and an analysis of the data, please see Ritter et al. (2017). The data available for either experiment are:• A video showing deformation in top view together with the evolution of boundary force. This file is in AVI-format.• A time-series of 2D vector fields describing the surface deformation. These vector fields were obtained from top-view video images of the respective experiment by means of digital image correlation (DIC). Each vector field is contained in a separate file; the files are consecutively numbered. The vector fields are stored in *.mat-files that can be opened using e.g. the software Matlab or the freely available GNU Octave. They take the form of Matlab structure arrays and are compatible to the PIVmat-toolbox by Moisy (2016) that is freely available. The most important fields of the structure are: x and y, that are vectors spanning a coordinate system, and vx and vy, which are arrays containing the actual vector components in x- and y-direction, respectively.• A file containing the measurements of the boundary force applied to drive deformation. This file is also a *.mat-file, containing a structure F with fields force, velocity and position. These fields are vectors describing the force applied by the indenter, the indenter velocity and the indenter position
# 6
Brizzi, Silvia • Funiciello, Francesca • Corbi, Fabio • Di Giuseppe, Erika • Mojoli, Giorgio
Abstract: Gelatin is a versatile material commonly used in analogue modelling because of its complex rheology, which allows simulating a wide range of tectonic processes requiring either elastic (e.g., dyke intrusions models) and viscoelastic behavior (e.g., analog earthquakes models). Salt (NaCl) is generally added to gelatin to improve the scaling of the models by increasing the density of the material. The addition of salt results also in a weakening of the gelatin structure, which in turn can dramatically affect its rheological properties. Here, we provide raw data of rheometric measurements performed to test the rheological properties of type A (pig-skin) 2.5 wt% gelatin at T=10°C as a function of salt concentration and ageing time. Each sample was analyzed using dynamical oscillation tests (i.e., amplitude, frequency and time sweep tests) in shear strain controlled mode. All details about sample preparation procedure, measuring protocol, as well as results and data interpretation can be found in Brizzi et al. (2016). The data are provided as Excel files in *.xlsx format and comma-separated files in *.csv format. Each contains multiple measurements. In the Excel files, each measurement is presented as a table in different spreadsheets. In the comma-separated files, each measurement start with its own data series information, followed by the actual data. All files can be opened using MS Excel or equivalent software. An overview of tested salt concentrations and performed measurements can be found in the Explanation_Brizzi_et_al_2016.pdf file. A full list of the files included is given in List_of_files_Brizzi_et_al_2016.pdf.
# 7
Souloumiac, Pauline • Maillot, Bertrand • Herbert, Justin W. • McBeck, Jessica A. • Cooke, Michele L.
Abstract: The data set includes photos, force measurements, and incremental displacement fields captured in experiment E240 run at the physical modeling laboratory (GEC) at the Université de Cergy-Pontoise. We built the accretionary wedge using a novel sedimentation device [Maillot, 2013] that distributes sand in planar layers and creates homogeneous sandpacks. We include photos of the side of the accretionary wedge in a zipped folder (E240_sideviews). Throughout the experiment, we took a photo every 5 seconds. We include the incremental displacement fields calculated from digital image correlation of sequential photos [Adam et al., 2005; Hoth, 2005] as matlab (.mat) files in a zipped folder (E240_001-062_DIC_MAT), and as .csv files in a zipped folder (E240_001-062_DIC_CSV). The .mat and .csv files are numbered to indicate which sequential photo pairs were used to calculate the displacements. For example, E240_001-062_0001_CSV.csv (and E240_001-062_0001.mat) contain the incremental displacements between photo 001.jpg and 002.jpg. All files are included in a single zip folder (Souloumiac-et-al-2017-supplementary-datasets.zip). The matlab files include the variable arrays x, y, u, v, which are the x and y coordinates (in pixels relative to the upper left corner of the image), and the horizontal (u) and vertical (v) incremental displacement fields (in pixels), respectively. The .csv files contain four columns of data with the x and y coordinates in the first two columns, and the horizontal (u) and vertical (v) displacements in the last two columns. We include force measurements in a text file (E240_force_corrected) with two columns: the first column is the total displacement of the backwall in millimeters at the time that the force measurement was recorded, and the second column is the normal force exerted on the backwall, in Newtons. The force measurements are calculated from measurements of strain gauges mounted on a wall of the sand box (i.e., the backwall) [e.g., Souloumiac et al., 2012].
# 8
Verberne, Berend Antonie • Chen, Jianye • Pennock, Gillian
Abstract: The largest magnitude earthquakes nucleate at depths near the base of the seismogenic zone, near the transition from velocity weakening frictional slip to velocity strengthening ductile flow. However, the mechanisms controlling this transition, and relevant to earthquake nucleation, remain poorly understood. Here we present data from experiments investigating the effect of slip rate on the mechanical properties and microstructure development of simulated calcite fault gouge sheared at ~550°C, close to the transition from (unstable) velocity weakening to (stable) velocity strengthening behaviour, reported by Verberne et al. (2015). We conducted experiments at a constant effective normal stress (σneff) of 50 MPa, as well as σneff-stepping tests employing 20 MPa ≤ σneff ≤ 140 MPa, at constant sliding velocities (v) of 0.1, 1, 10, or 100 µm/s. Samples sheared at v ≥ 1 µm/s showed a microstructure characterized by a single, 30 to 40 μm wide boundary shear, as well as a linear correlation of shear strength (τ) with σneff. Remarkably, electron backscatter diffraction mapping of polygonal shear band grains demonstrated a crystallographic preferred orientation. By contrast, samples sheared at 0.1 µm/s showed a microstructure characterized by homogeneous deformation and plastic flow, as well as a flattening-off of the τ-σneff curve. Our results point to a strain rate dependent frictional-to-viscous transition in simulated calcite fault gouge, and have important implications for the processes controlling earthquake nucleation at the base of the seismogenic zone.
# 9
Niemeijer, Andre
Abstract: The Alpine Fault, New Zealand, is a major plate-bounding fault that accommodates 65–75% of the total relative motion between the Australian and Pacific plates. Here we present data on the hydrothermal frictional properties of Alpine Fault rocks that surround the principal slip zones (PSZ) of the Alpine Fault and those comprising the PSZ itself. The samples were retrieved from relatively shallow depths during phase 1 of the Deep Fault Drilling Project (DFDP-1) at Gaunt Creek. Simulated fault gouges were sheared at temperatures of 25, 150, 300, 450, and 600°C in order to determine the friction coefficient as well as the velocity dependence of friction. Friction remains more or less constant with changes in temperature, but a transition from velocity-strengthening behavior to velocity-weakening behavior occurs at a temperature of T = 150°C. The transition depends on the absolute value of sliding velocity as well as temperature, with the velocity-weakening region restricted to higher velocity for higher temperatures.Friction was substantially lower for low-velocity shearing (V<0.3 μm/s) at 600°C, but no transition to normal stress independence was observed. In the framework of rate-and-state friction, earthquake nucleation is most likely at an intermediate temperature of T = 300°C. The velocity-strengthening nature of the Alpine Fault rocks at higher temperatures may pose a barrier for rupture propagation to deeper levels, limiting the possible depth extent of large earthquakes. Our results highlight the importance of strain rate in controlling frictional behavior under conditions spanning the classical brittle-plastic transition for quartzofeldspathic compositions. The data is provided in a .zip folder with 33 subfolders for 33 samples. Detailed information about the files in these subdfolders as well as sensors used, conversions and data specifications is given in the explanatory file Niemeijer-2017-DFDP-explanation-of-folder-structure-and-file-list.pdf.
# 10
Hunfeld, Luuk • Niemeijer, André • Spiers, Christopher
Abstract: We investigated the frictional properties of simulated fault gouges derived from the main lithologies present in the seismogenic Groningen gas field (NE Netherlands), employing in-situ P-T conditions and varying pore fluid salinity. Direct shear experiments were performed on gouges prepared from the Carboniferous Shale/Siltstone underburden, the Upper Rotliegend Slochteren Sandstone reservoir, the overlying Ten Boer Claystone, and the Basal Zechstein anhydrite-carbonate caprock, at 100 ºC, 40 MPa effective normal stress, and sliding velocities of 0.1-10 µm/s. As pore fluids, we used pure water, 0.5-6.2 M NaCl solutions, and a 6.9 M mixed chloride brine mimicking the formation water. Our results show a mechanical stratigraphy, with a maximum friction coefficient (µ) of ~0.65 for the Basal Zechstein, a minimum of ~0.37 for the Ten Boer claystone, ~0.6 for the reservoir sandstone, ~0.5 for the Carboniferous, and µ-values between the end-members for mixed gouges. Pore fluid salinity had no effect on frictional strength. Most gouges showed velocity-strengthening behavior, with little effect of pore fluid salinity on (a-b). However, Basal Zechstein gouge showed velocity-weakening at low salinities and/or sliding velocities, as did 50:50 mixtures with sandstone gouges, tested with the 6.9 M reservoir brine. From a Rate-and-State-Friction viewpoint, our results imply that faults incorporating Basal Zechstein anhydrite-carbonate material at the top of the reservoir are the most prone to accelerating slip, i.e. have the highest seismogenic potential. The results are equally relevant to other Dutch Rotliegend fields and to similar sequences globally. The data is provided in a .zip folder with 29 subfolders for 29 experiments/samples. Detailed information about the files in these subfolders as well as information on how the data is processed is given in the explanatory file Hunfeld-et-al-2017-Data-Description.pdf
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